PAM PAM8404

PAM8404
3W/CH Filterless Stereo Class-D Audio Amplifier
Features
Description
n 3W Output at 10% THD with a 4 Ω Load and
5V Supply
n Supply Voltage from 2.5V to 5.5 V
n Efficiency Up to 89%
n Superior Low Noise without Input
n Few External Components to Save the Space
and Cost
n Short Circuit Protection
n Thermal Shutdown
n Space Saving Packages :
2mm X 2mm WCSP
4mm X 4mm Thin QFN
n Pb-Free Packages
The PAM8404 is a 3W high efficiency filterless
class-D audio amplifier in 4mmX4mm QFN and
2mmX2mm wafer chip scale (WCSP) packages
that requires few external components.
Features like 89% efficiency, -63dB PSRR,
improved RF-rectification immunity, and very
small PCB area make the PAM8404 class-D
amplifier ideal for cellular handset and PDA
applications.
In cellular handsets, the earpiece, speaker phone,
and melody ringer can each be driven by the
PAM8404 . The PAM8404 allows independent gain
by summing signals from seperate sources, and
has as low as 43 μ V A-weighted noise floor.
Applications
n
n
n
n
n
LCD Monitor / TV Projector
Notebook Computers
Portable Speakers
Portable DVD Players, Game Machines
Cellular Phones/Speaker Phones
PAM8404 is available in QFN 4mmx4mm and
WCSP 2mmx2mm packages.
Typical Application Circuit
VDD
10μF
1μF
PVDD
PGND
Radiated Emissions
0.22μF
INR+
OUTR+
INR+
INR-
INR0.22μF
OUTR-
FCC Class B Limit
ON
SDR
OFF
G1
G1
G0
G0
PAM8404
ON
SDL
OFF
0.22μF
INL+
OUTL+
INL+
INL-
OUTL-
INL0.22μF
AVDD
AGND
1μF
VDD
10μF
Power Analog Microelectronics , Inc
www.poweranalog.com
03/2009 Rev 1.1
1
PAM8404
3W/CH Filterless Stereo Class-D Audio Amplifier
Block Diagram
V DD
To Battery
CS
OUTR+
INR+
Gain
Adjust
+ - +
PAM
Modulation
HBridge
OUTR-
INR-
GND
Internal
Oscillator
OUTL+
INL+
Gain
Adjust
+ - +
PAM
Modulation
HBridge
INL-
OUTL-
G0
G1
Short-Circuit
Protection
SDR
300kΩ
Bandgap
OTP
SDL
300kΩ
Power Analog Microelectronics , Inc
www.poweranalog.com
03/2009 Rev 1.1
2
PAM8404
3W/CH Filterless Stereo Class-D Audio Amplifier
Pin Configuration & Marking Information
QFN 4mmx4mm
Top View
INL+
PVDD
OUTL+
OUTL-
20
19
18
17
16
INR+
A4
INR-
A3
AGND
A2
INL-
A1
INL+
WCSP 2mmx2mm
Top View
1 G1
AVDD
OUTR+
2 OUTL+
3 PVDD
PGND
OUTR-
OUTR+ 14
P8404
XXXYW
PVDD 13
4 PGND
PGND 12
5 OUTL-
OUTR- 11
FR
YW
NC
AGND
G0
SDL
AVDD
INR+
SDR
SDR
D1
INR-
G1
SDL
C1
INL-
NC
B1
G0 15
6
7
8
9
10
FR: Product Code
of PAM8404
X: Internal Code
Y: Year
W: Week
(Marking)
Pin Descriptions
Name
G1
Pin Number
1
B2
Description
Gain select (MSB)
OUTL+
2
A3
Left channel positive differential output
PVDD
3,13
A2
Power supply (must be same voltage as AVDD)
PGND
4,12
C4
Power ground
OUTL-
5
A4
Left channel negative differential output
NC
6,10
-
SDL
7
B4
Left channel shutdown terminal (active low)
SDR
8
B3
Right channel shutdown terminal (active low)
AVDD
9
D2
Analog supply (must be same voltage as PVDD)
OUTR-
11
D4
Right channel negative differential output
OUTR+
14
D3
Right channel positive differential output
G0
15
C2
Gain select (LSB)
INR+
16
D1
Right channel positive input
INR-
17
C1
Right channel negative input
AGND
18
C3
Analog ground
INL-
19
B1
Left channel negative input
INL+
20
A1
Left channel positive input
No connect
Power Analog Microelectronics , Inc
www.poweranalog.com
03/2009 Rev 1.1
3
PAM8404
3W/CH Filterless Stereo Class-D Audio Amplifier
Absolute Maximum Ratings
These are stress ratings only and functional operation is not implied. Exposure to absolute maximum
ratings for prolonged time periods may affect device reliability. All voltages are with respect to ground.
Supply Voltage . ...........................................6.0V
Input Voltage.............................-0.3V to V DD+0.3V
Maximum Junction Temperature..................150°C
Storage Temperature.....................-65 °C to 150 °C
Soldering Temperature.................... 250°C,10 sec
Recommended Operating Conditions
Supply voltage Range........................ 2.5V to 5.5V
Operation Temperature Range.........-40 °C to 85 °C
Junction Temperature Range.........-40 °C to 125 °C
Thermal Information
Parameter
Symbol
Thermal Resistance (Junction to Ambient)
θJA
Thermal Resistance (Junction to Case)
θJC
Package
Maximum
WCSP2x2-16
64
QFN4x4-20
31
WCSP2x2-16
-
QFN4x4-20
13
Unit
°C/W
°C/W
Power Analog Microelectronics , Inc
www.poweranalog.com
03/2009 Rev 1.1
4
PAM8404
3W/CH Filterless Stereo Class-D Audio Amplifier
Electrical Characteristic
QFN 4x4 20-Pin
T A=25 °C, AVDD=PVDD=5V, GND=PGND=0V, unless otherwise noted.
Parameter
Supply Voltage
Symbol
Test Conditions
VDD
2.5
THD+N=10% f=1kHz RL=4Ω
THD+N=1% f=1kHz R L=4Ω
Output Power
PO
THD+N=10% f=1kHz RL=8Ω
THD+N=1% f=1kHz R L=8Ω
VDD =5.0V,Po=0.5W,RL=8Ω
Total Harmonic Distortion Plus
Noise
THD+N
VDD =3.6V,Po=0.5W,RL=8Ω
VDD =5.0V,Po=1W,R L=4Ω
VDD =3.6V,Po=1W,R L=4Ω
Power Supply Ripple
Rejection
Crosstalk
Signal-to-noise ratio
PSRR
Cs
SNR
Dynamic range
Vn
Dyn
Efficiency
η
Quiescent Current
IQ
Shutdown Current
ISD
Static Drain-to-source
On-state Resistor
Rdson
VDD =5V
5.5
3
VDD =3.6V
1.5
VDD =5V
2.35
VDD =3.6V
1.2
VDD =5V
1.7
VDD =3.6V
0.9
VDD =5V
1.4
VDD =3.6V
0.7
f=1kHz
f=1kHz
0.15
0.27
0.23
0.24
VDD =5.0V, Inputs ac-grounded with f=100Hz
-48
Cin=1μF
-63
f=1kHz
V
W
W
W
W
%
%
dB
VDD =5V,Po=0.5W,R L=4Ω,Gv=23dB F=1kHz
-93
dB
VDD =5V, Vorms=1V,Gv=23dB
A-weighting
87
dB
A-weighting
43
BW 22Hz-22kHz
No A-weighting
59
VDD =5.0V, THD=1%
A-weighting
97
VDD =5V, Inputs ac-grounded with
Output noise
MIN TYP MAX UNIT
Cin=1μF
RL=8Ω, THD=10%
RL=4Ω, THD=10%
VDD =5V
f=1kHz
No load
VDD =3.6V
VDD =5.5V
IDS=500mA,Vgs=5V
89
84
11
6
Vsd=0.3V
<1
PMOS
250
NMOS
170
μV
dB
%
mA
μA
mΩ
Switching Frequency
fsw
VDD =3V to 5V
300
kHz
Output Offset Voltage
Vos
Vin=0V, V DD =5V
10
mV
closed-loop voltage gain
Over Temperature Protection
Gain
VDD =5V RL=4Ω f=1kHz
OTP
G0=L G1=L
6
G0=H G1=L
12
G0=L G1=H
18
G0=H G1=H
24
150
No Load, Junction Temperature
Over Temperature Hysterisis
dB
OTH
°C
50
Power Analog Microelectronics , Inc
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03/2009 Rev 1.1
5
PAM8404
3W/CH Filterless Stereo Class-D Audio Amplifier
Electrical Characteristic
WCSP 2x2-16
T A=25 °C, AVDD=PVDD=5V, GND=PGND=0V, unless otherwise noted.
Parameter
Supply Voltage
Symbol
Test Conditions
VDD
2.5
THD+N=10% f=1kHz RL=4Ω
THD+N=1% f=1kHz RL=4Ω
Output Power
PO
THD+N=10% f=1kHz RL=8Ω
THD+N=1% f=1kHz RL=8Ω
VDD =5.0V,Po=0.5W,RL =8Ω
Total Harmonic Distortion Plus
Noise
THD+N
VDD =3.6V,Po=0.5W,RL =8Ω
VDD =5.0V,Po=1W,RL=4Ω
VDD =3.6V,Po=1W,RL=4Ω
Power Supply Ripple
Rejection
Crosstalk
Signal-to-noise ratio
PSRR
Cs
SNR
VDD =5.0V, Inputs ac-grounded with
Dynamic range
Vn
Dyn
Efficiency
η
Quiescent Current
IQ
Shutdown Current
ISD
Static Drain-to-source
On-state Resistor
Rdson
5.5
VDD =5V
2.2
VDD =3.6V
1.2
VDD =5V
1.8
VDD =3.6V
1
VDD =5V
1.5
VDD =3.6V
0.8
VDD =5V
1.2
VDD =3.6V
0.6
f=1kHz
f=1kHz
0.4
0.3
0.2
W
W
W
W
%
%
dB
VDD =5V,Po=0.5W,RL=4Ω,Gv=23dB f=1kHz
-70
dB
VDD =5V, Vorms=1V,Gv=23dB
A-weighting
85
dB
A-weighting
34
BW 22Hz-22kHz
No A-weighting
54
VDD =5.0V, THD=1%
A-weighting
98
Cin=1μF
RL=8Ω, THD=10%
RL=4Ω, THD=10%
VDD =5V
f=217Hz
0.3
V
-50
Cin=1μF
VDD =5V, Inputs ac-grounded with
Output noise
MIN TYP MAX UNIT
f=1kHz
No load
VDD =3.6V
VDD =2.5V to 5.5V
IDS=500mA,Vgs=5V
85
75
12
7
Vsd=0.3V
<1
PMOS
500
NMOS
460
μV
dB
%
mA
μA
mΩ
Switching Frequency
fsw
VDD =5V
300
kHz
Output Offset Voltage
Vos
Vin=0V, V DD =5V
20
mV
closed-loop voltage gain
Over Temperature Protection
Gain
VDD =5V RL=4Ω f=1kHz
OTP
G0=L G1=L
6
G0=H G1=L
12
G0=L G1=H
18
G0=H G1=H
24
150
No Load, Junction Temperature
Over Temperature Hysterisis
dB
OTH
°C
50
Power Analog Microelectronics , Inc
www.poweranalog.com
03/2009 Rev 1.1
6
PAM8404
3W/CH Filterless Stereo Class-D Audio Amplifier
Typical Operating Characteristics (T =25°C)
A
QFN 4x4 20-Pin
Efficiency vs Output Power
R L=8 Ω, V DD=5V, L =33 μ H
100
90
90
80
80
70
70
Efficiency(%)
Efficiency(%)
100
Efficiency vs Output Power
R L=4 Ω, V DD=5V, L =33 μ H
60
50
40
60
50
40
30
30
20
20
10
10
0
200
400
600
800
1000 1200 1400 1600 1800
0
300 600 900 1200 1500 1800 2100 2400 2700 3000
Output Pow er(mW)
Output Pow er(mW)
THD+N vs Output Power
R L=4 Ω , Gain=23dB, f=1kHz
THD+N vs Output Power
R L=8 Ω , Gain=23dB, f=1kHz
30
30
VDD=5V
VDD=5V
10
5
10
5
VDD=3.6V
2
2
VDD =2.5V
1
%
VDD=3.6V
VDD =2.5V
1
%
0.5
0.5
0.2
0.2
0.1
0.1
0.05
0.05
0.02
0.02
0.01
10m
20m
50m
100m
200m
500m
1
2
0.01
10 m
4
20 m
50 m
100m
30
20
200m
500m
THD+N vs Frequency
P O=0.5W, R L=8 Ω , C IN=1 μ F,Gain=23dB
30
20
10
10
5
5
2
%
2
4
VDD =3.6V
1
%
0.5
0.2
0.5
0.2
0.1
0.1
0.05
0.05
VDD =5V
0.02
0.01
20
2
THD+N vs Frequency
P O=0.5W, R L=4 Ω , C IN=1 μ F,Gain=23dB
VDD =3.6V
VDD =5.5V
1
1
W
W
VDD =5V
VDD =5.5V
0.02
50
100
200
500
1k
2k
5k
10k
0.01
20
20k
Hz
50
100
200
500
1k
2k
5k
10k
20k
Hz
Power Analog Microelectronics , Inc
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03/2009 Rev 1.1
7
PAM8404
3W/CH Filterless Stereo Class-D Audio Amplifier
Typical Operating Characteristics (T =25°C)
A
QFN 4x4 20-Pin
THD+N vs Frequency
V DD=5V, R L=4 Ω , C IN=1 μ F,Gain=23dB
THD+N vs Frequency
V DD=5V, R L=8 Ω , C IN=1 μ F,Gain=23dB
30
20
30
20
10
10
5
5
PO=1W
2
PO =1.3W
1
%
PO=1W
2
1
%
0.5
0.2
PO=0.5W
0.5
0.2
PO=0.5W
0.1
0.1
0.05
0.05
0.02
0.02
0.01
20
50
100
200
500
1k
2k
5k
10k
0.01
20
20k
PO =2W
50
100
200
Hz
500
1k
2k
5k
10k
20k
10 k
20 k
Hz
Frequency Response
V DD=5V, R L=4 Ω , C IN=1 μ F
+25
+0
PSSR vs Frequency
Input ac-ground, V DD=5V 200mVpp,
R L=4 Ω , C IN=1 μ F, gain=16dB
G0=1G1=1
+22.5
-10
+20
-20
+17.5
A
-30
G0=0 G1=1
d +15
B
r +12.5
-40
d
B
G0=1G1=0
+10
R
-50
-60
+7.5
-70
G0=0 G1=0
+5
-80
+2.5
-90
+0
20
50
100
200
500
1k
2k
5k
L
-100
20
10k 20k
50
100
200
1k
2k
5k
Noise Floor FFT
Inputs ac-ground, V DD=5V, C IN=1 μ F, R L=4 Ω ,
Gain=23dB
Crosstalk vs Frequency
V DD=5V, R L=4 Ω , Gain=23dB
-65
500
Hz
Hz
-50
T T
-70
-60
-75
-80
-70
R to L
-85
d
B
d
B
r
-90
-95
-80
L
-90
A
-100
-100
-105
-110
L to R
-110
-115
-120
20
R
50
100
200
500
1k
2k
5k
10k
-120
20
20k
Hz
50
100
200
500
1k
2k
5k
10k 20k
Hz
Power Analog Microelectronics , Inc
www.poweranalog.com
03/2009 Rev 1.1
8
PAM8404
3W/CH Filterless Stereo Class-D Audio Amplifier
Typical Operating Characteristics (T =25°C)
A
QFN 4x4 20-Pin
16
Quiescent Current vs Supply Voltage
No Input, R L=No Load
Frequency vs Supply Voltage
Input ac-ground
300
296
12
Frequency(KHz)
Quiescent Current(mA)
14
10
8
6
4
292
288
284
2
0
280
2
2.5
3
3.5
4
4.5
5
5.5
6
2
2.5
3
Pow er Supply Voltage(V)
3.5
4
4.5
5
5.5
6
5.5
6
Pow er Supply Voltage(V)
Output Power vs Supply Voltage
C IN=1 μ F, R L=4 Ω , Gain=23dB, f=1kHz
Output Power vs Supply Voltage
C IN=1 μ F, R L=8 Ω , Gain=23dB, f=1kHz
4
2.5
3.5
3
Output Power(w)
Output Power(w)
2
10%
1.5
1
1%
2.5
10%
2
1.5
1%
1
0.5
0.5
0
0
2
2.5
3
3.5
4
4.5
5
5.5
6
2
Pow er Supply Voltage(V)
2.5
3
3.5
4
4.5
5
Pow er Supply Voltage(V)
Power Analog Microelectronics , Inc
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03/2009 Rev 1.1
9
PAM8404
3W/CH Filterless Stereo Class-D Audio Amplifier
Typical Operating Characteristics (T =25°C)
A
WCPS 2x2-16
Efficiency vs Output Power
R L=8 Ω, V DD=5V, L =22 μ H
100
80
90
70
80
Efficiency(%)
Efficiency(%)
90
Efficiency vs Output Power
R L=4 Ω, V DD=5V, L =22 μ H
60
50
40
70
60
50
40
30
30
20
20
10
10
0
200
400
600
800
1000 1200
1400 1600
0
300
600
Output Pow er(mW)
30
900
1200 1500
Output Pow er(mW)
THD+N vs Output Power
R L=4 Ω , Gain=23dB, f=1kHz
THD+N vs Output Power
R L=8 Ω , Gain=23dB, f=1kHz
30
20
VDD=5.5V
10
VDD=5.5V
10
VDD=5V
5
VDD=5V
5
%
1800 2100 2400
2
VDD =3.6V
1
VDD =3.6V
2
%
1
0.5
0.2
0.1
0.5
0.05
0.2
0.02
0.1
10m
20m
50m
100m
200m
500m
1
2
0.01
10m
4
20m
50m
100m
W
30
20
10
10
5
5
1
%
0.5
0.2
4
VDD =3.6V
0.5
0.2
VDD =5V
0.1
0.05
0.02
0.02
50
100
200
500
Hz
1k
2k
VDD =5V
0.1
0.05
0.01
20
2
VDD =5.5V
2
VDD =3.6V
1
%
1
THD+N vs Frequency
P O=0.5W, R L=4 Ω , C IN=1 μ F,Gain=23dB
30
20
VDD =5.5V
500m
W
THD+N vs Frequency
P O=0.5W, R L=8 Ω , C IN=1 μ F,Gain=23dB
2
200
m
5k
10k
0.01
20
20k
50
100
200
500
1k
2k
5k
10k
20k
Hz
Power Analog Microelectronics , Inc
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03/2009 Rev 1.1
10
PAM8404
3W/CH Filterless Stereo Class-D Audio Amplifier
Typical Operating Characteristics (T =25°C)
A
WCPS 2x2-16
THD+N vs Frequency
V DD=5V, R L=8 Ω , C IN=1 μ F, Gain=23dB
30
20
30
20
10
10
5
5
PO=1.2W
PO =1 W
2
PO =1.8W
2
1
%
THD+N vs Frequency
V DD=5V, R L=4 Ω , C IN=1 μ F, Gain=23dB
1
%
0.5
0.5
0.2
0.2
0.1
0.1
PO=0.5W
0.05
0.05
0.02
0.02
0.01
20
50
100
200
500
1k
2k
5k
10k
0.01
20
20k
PO=0.5W
PO=1.2W
50
100
200
500
Hz
Hz
1k
2k
5k
10k
20k
10k
20k
PSSR vs Frequency
Input ac-ground, V DD=5V 200mVpp,
R =4 Ω , C IN=1 μ F, gain=5dB
+0 L
Frequency Response
V DD=5V, R L=4 Ω , C IN=1 μ F
+25
G0=1 G1=1
+22.5
-10
-20
+20
-30
+17.5
d
+15
B
r +12.5
A
G0= 0 G1=1
R
-40
d
B
G0=1 G1= 0
-50
-60
+10
-70
+7.5
G0= 0 G1= 0
+5
L
-80
+2.5
-90
+0
20
50
100
200
500
1k
2k
5k
10
k
-100
20
20k
50
100
200
500
1k
2k
5k
Hz
Hz
Noise Floor FFT
Inputs ac-ground, V DD=5V, C IN=1 μ F, R L=4 Ω ,
Gain=23dB
-50
Crosstalk vs Frequency
V DD=5V, R L=4 Ω , Gain=23dB
-50
-55
-60
-60
R to L
-70
-65
R
-80
-70
d
B
-75
d
B
r
-80
A
-90
-100
-85
L to R
-110
-90
-120
-95
-100
20
50
100
200
500
1k
2k
5k
10k
-130
20
20k
L
50
100
200
500
1k
2k
5k
10 k
20 k
Hz
Hz
Power Analog Microelectronics , Inc
www.poweranalog.com
03/2009 Rev 1.1
11
PAM8404
3W/CH Filterless Stereo Class-D Audio Amplifier
Typical Operating Characteristics (T =25°C)
A
WCPS 2x2-16
Quiescent Current vs Supply Voltage
No Input, R L=No Load
Frequency vs Supply Voltage
Input ac-ground
16
304
300
12
Frequency(KHz)
Quiescent Current(mA)
14
10
8
6
4
296
292
288
2
0
284
2
2.5
3
3.5
4
4.5
5
5.5
6
2
2.5
3
Output Power vs Supply Voltage
C IN=1 μ F, R L=8 Ω , Gain=23dB, f=1kHz
3
4.5
5
5.5
6
5.5
6
Output Power vs Supply Voltage
C IN=1 μ F, R L=4 Ω , Gain=23dB, f=1kHz
2.5
Output Power(w)
1.6
Output Power(w)
4
Pow er Supply Voltage(V)
Pow er Supply Voltage(V)
2
3.5
10%
1.2
0.8
1%
0.4
2
10%
1.5
1
1%
0.5
0
0
2
2.5
3
3.5
4
4.5
5
5.5
6
2
Pow er Supply Voltage(V)
2.5
3
3.5
4
4.5
5
Pow er Supply Voltage(V)
Power Analog Microelectronics , Inc
www.poweranalog.com
03/2009 Rev 1.1
12
PAM8404
3W/CH Filterless Stereo Class-D Audio Amplifier
Test Setup for Performance Testing
PAM8404 Demo Board
Load
+OUT
AP System One
Generator
Input
AP
Low Pass
Filter
GND
-OUT
AP System One
Analyzer
AUX-0025
VDD
Power Supply
Notes
1. The AP AUX-0025 low pass filter is necessary for class-D amplifier measurement with AP analyzer.
2. Two 22μH inductors are used in series with load resistor to emulate the small speaker for efficiency
measurement.
Power Analog Microelectronics , Inc
www.poweranalog.com
03/2009 Rev 1.1
13
PAM8404
3W/CH Filterless Stereo Class-D Audio Amplifier
Application Information
Gain Settin
For this reason, a low-leakage tantalum or
ceramic capacitor is the best choice. When
polarized capacitors are used, the positive side of
the capacitor should face the amplifier input in
most applications as the DC level is held at V DD/2,
which is likely higher than the source DC level.
Please note that it is important to confirm the
capacitor polarity in the application.
The gain of PAM8404 can be selected as 6,12,18
or 24 dB utilizing the G0 and G1 gain setting pins.
The gains showed in the following table are
realized by changing the input resistors inside the
amplifier. The input impedance changes with the
gain setting.
0
0
2
6
28.1
If the corner frequency is within the audio band,
the capacitors should have a tolerance ±10% or
better, because any mismatch in capacitance
cause an impedance mismatch at the corner
frequency and below.
0
1
4
12
17.3
Decoupling Capacitor (CS)
1
0
8
18
9.8
1
1
16
24
5.2
Table-1: Gain Setting
G1
G0
GAIN
GAIN
INPUT IMPEDANCE
(V/V)
(dB)
(kΩ)
The PAM8404 is a high-performance CMOS audio
amplifier that requires adequate power supply
decoupling to ensure the output total harmonic
distortion (THD) as low as possible. Power supply
decoupling also prevents the oscillations causing
by long lead length between the amplifier and the
speaker.
For optimal performance the gain should be set to
2x (Ri=150k Ω ). Lower gain allows the PAM8404
to operate at its best, and keeps a high voltage at
the input making the inputs less susceptible to
noise. In addition to these features, lower value of
Gain minimizes pop noise.
The optimum decoupling is achieved by using two
different types of capacitors that target on
different types of noise on the power supply
leads. For higher frequency transients, spikes, or
digital hash on the line, a good low equivalentseries-resistan ce (ESR) ceramic capacitor,
typically 1μF, is placed as close as possible to the
device each VDD and PVDD pin for the best
operation. For filtering lower frequency noise
signals, a large ceramic capacitor of 10μF or
greater placed near the audio power ampl ifier is
recommended.
Input Capacitors (Ci )
In the typical application, an input capacitor, Ci, is
required to allow the amplifier to bias the input
signal to the proper DC level for optimum
operation. In this case, Ci and the input
impedance Ri form a high-pass filter with the
corner frequency determined by the follow
equation:
1
fC =
(2p RiCi)
How to Reduce EMI
It is important to consider the value of Ci as it
directly affects the low frequency performance of
the circuit. When Ri is 28.1kΩ and the
specification calls for a flat bass response are
down to 200Hz, the equation is reconfigured as
follows:
1
Ci =
(2p Rifc )
Most applications require a ferrite bead filter for
EMI elimination as shown at Figure 1. The ferrite
filter reduces EMI of around 1MHz and higher.
When selecting a ferrite bead, choose one with
high impedance at high frequencies and low
impedance at low frequencies.
Ferrite Bead
OUT+
When input resistance variation is considered,
the Ci is 28nF, so one would likely choose a value
of 33nF. A further consideration for this capacitor
is the leakage path from the input source through
the input network (Ci, Ri + Rf) to the load. This
leakage current creates a DC offset voltage at the
input to the amplifier that reduces useful
headroom, especially in high gain applications.
220pF
Ferrite Bead
OUT220pF
Figure 1: Ferrite Bead Filter to Reduce EMI
Power Analog Microelectronics , Inc
www.poweranalog.com
03/2009 Rev 1.1
14
PAM8404
3W/CH Filterless Stereo Class-D Audio Amplifier
Shutdown operation
PCB Layout Guidelines
In order to reduce power consumption while not in
use, the PAM8404 contains shutdown circuitry to
turn off the amplifier's bias circuitry. It features
independent shutdown controls for each channel.
This shutdown turns the amplifier off when logic
low is placed on the SDx pin. By switching the
shutdown pin to GND, the PAM8404 supply
current draw will be minimized in idle mode.
Grounding
It is recommended to use plane grounding or
separate grounds. Do not use one line connecting
power GND and analog GND. Noise currents in
the output power stage need to be returned to
output noise ground and nowhere else. When
these currents circulate elsewhere, they may get
into the power supply, or the signal ground, etc,
even worse, they may form a loop and radiate
noise. Any of these instances results in degraded
amplifier performance. The output noise ground
that the logical returns for the output noise
currents associated with class D switching must
tie to system ground at the power exclusively.
Signal currents for the inputs, reference need to
be returned to quite ground. This ground only ties
to the signal components and the GND pin. GND
then ties to system ground.
Short Circuit Protection (SCP)
The PAM8404 has short circuit protection circuitry
on the outputs to prevent the device from damage
when output-to-output shorts or output-to-GND
shorts occur. When a short circuit occurs, the
device immediately goes into shutdown state.
Once the short is removed, the device will be
reactivated.
Over Temperature Protection (OTP)
Power Supply Line
Thermal protection on the PAM8404 prevents the
device from damage when the internal die
temperature exceeds 150°C. There is a 15°C
tolerance on this trip point from device to device.
Once the die temperature exceeds the set point,
the device will enter the shutdown state and the
outputs are disabled. This is not a latched fault.
The thermal fault is cleared once the temperature
of the die decreased by 50°C. This large
hysteresis will prevent motor boating sound well
and the device begins normal operation at this
point with no external system interaction.
Same a s the ground, VDD and PVDD need to be
separately connected to the system power supply.
It is recommended that all the trace could be
routed as short and thick as possible. For the
power line layout, just imagine water stream, any
barricade placed in the trace (shown in figure 2)
could result in the bad performance of the
amplifier.
POP and Click Circuitry
Figure 2: Power Line
The PAM8404 contains circuitry to minimize turnon and turn-off transients or “click and pops”,
where turn-on refers to either power supply turnon or device recover from shutdown mode. When
the device is turned on, the amplifiers are
internally muted. An internal current source ramps
up the internal reference voltage. The device will
remain in mute mode until the reference voltage
reach half supply voltage V DD/2. As soon as the
reference voltage is stable, the device will begin
full operation. For the best power-off pop
performance, the amplifier should be set in
shutdown mode prior to removing the power
supply voltage.
Components Placement
Decoupling capacitors-As previously described,
the high-frequency 1μF decoupling capacitors
should be placed as close to the power supply
terminals (VDD and PVDD) as possible. Large
bulk power supply decoupling capacitors (10μF or
greater) should be placed near the PAM8 404 on
the PVDD terminal.
Input capacitors need to be placed very close to
input pins.
Output filter - The ferrite EMI filter should be
placed as close to the output terminals as
possible for the best EMI performance, and the
capacitors used in the filters should be grounded
to system ground.
Power Analog Microelectronics , Inc
www.poweranalog.com
03/2009 Rev 1.1
15
PAM8404
3W/CH Filterless Stereo Class-D Audio Amplifier
Ordering Information
PAM8404 X X X
Shipping Package (R: Tape & Reel)
Number of Pins (E: 16; G: 20)
Package Type (Z: WCSP; K: QFN4x4)
Part Number
PAM8404ZER
PAM8404KGR
Marking
FR
YW
P8404
XXXYW
Package Type
Shipping Package
WCSP 16
3,000 Units/Tape & Reel
QFN4x4 20L
3,000 Units/Tape & Reel
Power Analog Microelectronics , Inc
www.poweranalog.com
03/2009 Rev 1.1
16
PAM8404
3W/CH Filterless Stereo Class-D Audio Amplifier
Outline Dimensions
WCSP 2x2
1.00
1.95 ± 0.02
0.50
1.95 ± 0.02
Units:Millimeter
0.235 ± 0.02
0.415 ± 0.04
Power Analog Microelectronics , Inc
www.poweranalog.com
03/2009 Rev 1.1
17
PAM8404
3W/CH Filterless Stereo Class-D Audio Amplifier
Outline Dimensions
QFN4x4-20L
Power Analog Microelectronics , Inc
www.poweranalog.com
03/2009 Rev 1.1
18